The present invention relates to the area of digital networks for connecting a plurality of computers to form a computer network and more particularly to computer networks that utilize the telephone lines for the transmission of data therein.
Many businesses have computer networks which extend over large geographic areas. The most economical manner for implementing such networks utilizes existing telephone lines to connect the various computers in the network. Computer networks that utilize the telephone system are known to the prior art. However, these computer networks are less than ideal.
First, prior art computer networks are difficult to reconfigure either with regard to the speed at which data is transmitted within the telephone system or with regard to the topological configuration of the computer network. In prior art computer networks, telephone company technicians must be dispatched to various locations within the telephone system to affect a data rate change in the computer network. If the new data rate is not one of a small number of existing rates, the actual interface circuitry within the telephone system must often be changed. As a result, it is practically impossible to change data rates in response to short-term changes in the quality of the telephone lines carrying the data.
The telephone lines used for carrying the user's computer data are, in general, identical to the lines used to carry voice communications within the telephone system. These lines are bundled into cables with similar lines. The noise level on these lines depends upon a number of factors including the nature of the transmissions on adjacent lines in the cables. Since the traffic on the adjacent lines varies with time, the noise levels on the lines used for the computer network will, in general, vary with the time of day or the day of the week.
One method of reducing data errors resulting from increased noise on the telephone lines is to reduce the speed at which data is transmitted over these lines. However, given the difficulty in shifting the speed of prior art computer networks, this option is difficult, if not impossible, to implement in a practical manner. Hence, prior art computer networks are normally set up at a sufficiently low data rate to assure an acceptable data error rate. As a result, the increased capacity that is available during those times of the day at which the noise levels are reduced is not available.
In addition to being able to alter the speed in response to noise levels, it would be particularly advantageous to be able to change the topological configuration of the computer network. Such reconfiguration is useful in smoothing peak loads on the computer network. Such reconfigurability would also be useful in transferring specific services to offices in an earlier time zones when the office providing the service in another time zone closed at the end of the day. In prior art systems, such reconfiguration requires that key components of the computer network be rewired by telephone company personnel or that special purpose hardware be installed at significant cost.
Second, prior art computer networks do not allow the user to monitor and manage the computer network. If a failure occurs in the computer network, it often requires telephone company technicians to ascertain the location of the failure within the system. The time delays in waiting for such determinations to be made are often unacceptable. It would be advantageous to provide a means for allowing the network user to set loopbacks and other diagnostic aids within the computer network without the time delays and added expense inherent when telephone company personnel must be involved. Similarly, the computer network user would like to be able to access data showing error rates on the various communication links in the computer network. Such facilities are not provided by prior art computer networks that utilize the telephone system.
Broadly, it is an object of the present invention to provide an improved computer network that utilizes the telephone lines for communication among the computers therein.
It is a further object of the present invention to provide a computer network in which the speed of data transmission can be altered by the computer network user.
It is yet another object of the present invention to provide a computer network in which the speed of data transmission can be altered automatically in response to the observed transmission error rates in the computer network.
It is a still further object of the present invention to provide a computer network which allows automatic reconfiguration to a new topology without the need for rewiring system components.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.